1. Field of the Invention
The present invention relates to a carbonaceous composite material excellent in abrasion resistance and self-lubricating properties and having secondary corrosion inhibiting properties and to a sliding member using the same.
2. Description of the Related Art
Carbonaceous composite materials, which are excellent in chemical resistance, heat resistance and machinability as well as in self-lubricating properties, are regarded with interests as sliding members, for example, and are widely used, including electric sliding brushes for generators (hereinafter they are simply referred to as "brush"); bearings for various kinds of devices; and mechanical sealing rings. Recently, the devices are often used in even more harsh conditions or extreme environmental conditions and, besides, are demanded for high reliability and life extension. To meet the demands, the carbonaceous composite materials are growing in development. One of the carbonaceous composite materials, which have developed as part of the development, is a carbonaceous composite material to which graphite fluoride is added. It is known that the addition of graphite fluoride can largely contribute to improvement of abrasion resistance and self-lubricating properties of the carbonaceous composite materials and is particularly preferable as the sliding members (Japanese Laid-open Patent Publication No. Sho 55-116609).
However, the brushes made from the carbonaceous composite material in which graphite fluoride was added have been found to have great problems when actually assembled in a motor to use them. Those are the problems that in use, a decomposed product of the graphite fluoride produced in the brush, i.e., fluorine, escapes out and reacts with moisture (water) in the air to thereby produce hydrofluoric acid, which in turn can produce detrimental effects. Specifically, not only the event that the produced hydrofluoric acid causes corrosion of a commutator (made of copper) of the motor to progress in a short time but also the so-called secondary corrosion of various kinds of metallic members around the brush being corroded gradually are caused.
In addition, the graphite fluoride is very much expensive, so manufacturing costs for the sliding members are largely influenced by even a few percent of variations of the additive ratio. For this reason, it is necessary to determine the limits on the additive ratio of graphite fluoride so that high sliding performance can be obtained with a minimum additive ratio, for production of the sliding members of cost efficiency.
In the light of the circumstances mentioned above, the present invention has been made. It is the objective of the present invention to attempt to provide (i) a carbonaceous composite material that can fully provide the characteristic effect of the graphite fluoride containing carbonaceous composite material with a minimum additive ratio of graphite fluoride and simultaneously can provide the secondary corrosion inhibiting properties and (ii) a sliding member using the same.